A gas turbine is used as an apparatus that extracts energy from combustion gas obtained by burning fuel. A gas turbine rotates a turbine by using energy of combustion gas produced by burning fuel, and outputs rotation energy from a rotor.
For example, Patent document 1 discloses a technology for preventing thermal deformation of a chamber casing, by mounting a valve for supplying external air to the inside of an upper chamber casing, and by introducing the external air into the inside of the chamber casing from the upper chamber casing to cool the upper chamber casing while the operation performed by the gas turbine is stopped.    [Patent document 1] Japanese Patent Application Laid-open No. 2006-37855